diff -r 47288880cc9e Doc/library/string.rst
--- a/Doc/library/string.rst	Fri Feb 17 19:58:41 2012 -0500
+++ b/Doc/library/string.rst	Sat Feb 18 12:51:49 2012 +0100
@@ -91,8 +91,8 @@
 
    .. method:: format(format_string, *args, **kwargs)
 
-      :meth:`format` is the primary API method.  It takes a format template
-      string, and an arbitrary set of positional and keyword argument.
+      :meth:`format` is the primary API method.  It takes a format string and
+      an arbitrary set of positional and keyword arguments.
       :meth:`format` is just a wrapper that calls :meth:`vformat`.
 
    .. method:: vformat(format_string, args, kwargs)
@@ -101,8 +101,8 @@
       separate function for cases where you want to pass in a predefined
       dictionary of arguments, rather than unpacking and repacking the
       dictionary as individual arguments using the ``*args`` and ``**kwds``
-      syntax.  :meth:`vformat` does the work of breaking up the format template
-      string into character data and replacement fields.  It calls the various
+      syntax.  :meth:`vformat` does the work of breaking up the format string
+      into character data and replacement fields.  It calls the various
       methods described below.
 
    In addition, the :class:`Formatter` defines a number of methods that are
@@ -173,7 +173,8 @@
 
       Converts the value (returned by :meth:`get_field`) given a conversion type
       (as in the tuple returned by the :meth:`parse` method).  The default
-      version understands 'r' (repr) and 's' (str) conversion types.
+      version understands 's' (str), 'r' (repr) and 'a' (ascii) conversion
+      types.
 
 
 .. _formatstrings:
@@ -202,9 +203,9 @@
       conversion: "r" | "s" | "a"
       format_spec: <described in the next section>
 
-In less formal terms, the replacement field can start with a *field_name* that specifies
-the object whose value is to be formatted and inserted
-into the output instead of the replacement field.
+In less formal terms, the replacement field can start with a *field_name* that
+specifies the object whose value is to be formatted and inserted into the
+output instead of the replacement field.
 The *field_name* is optionally followed by a  *conversion* field, which is
 preceded by an exclamation point ``'!'``, and a *format_spec*, which is preceded
 by a colon ``':'``.  These specify a non-default format for the replacement value.
@@ -212,10 +213,10 @@
 See also the :ref:`formatspec` section.
 
 The *field_name* itself begins with an *arg_name* that is either a number or a
-keyword.  If it's a number, it refers to a positional argument, and if it's a keyword,
-it refers to a named keyword argument.  If the numerical arg_names in a format string
-are 0, 1, 2, ... in sequence, they can all be omitted (not just some)
-and the numbers 0, 1, 2, ... will be automatically inserted in that order.
+keyword.  If it's a number, it refers to a positional argument, and if it's a
+keyword, it refers to a named keyword argument.  If the numerical arg_names in
+a format string are 0, 1, 2, ... in sequence, they can all be omitted (not just
+some) and the numbers 0, 1, 2, ... will be automatically inserted in that order.
 Because *arg_name* is not quote-delimited, it is not possible to specify arbitrary
 dictionary keys (e.g., the strings ``'10'`` or ``':-]'``) within a format string.
 The *arg_name* can be followed by any number of index or
diff -r 47288880cc9e Lib/string.py
--- a/Lib/string.py	Fri Feb 17 19:58:41 2012 -0500
+++ b/Lib/string.py	Sat Feb 18 12:51:49 2012 +0100
@@ -195,7 +195,7 @@
 
                 # expand the format spec, if needed
                 format_spec = self._vformat(format_spec, args, kwargs,
-                                            used_args, recursion_depth-1)
+                                            used_args, recursion_depth - 1)
 
                 # format the object and append to the result
                 result.append(self.format_field(obj, format_spec))
@@ -220,12 +220,14 @@
 
     def convert_field(self, value, conversion):
         # do any conversion on the resulting object
-        if conversion == 'r':
-            return repr(value)
+        if conversion is None:
+            return value
         elif conversion == 's':
             return str(value)
-        elif conversion is None:
-            return value
+        elif conversion == 'r':
+            return repr(value)
+        elif conversion == 'a':
+            return ascii(value)
         raise ValueError("Unknown conversion specifier {0!s}".format(conversion))
 
 
diff -r 47288880cc9e Lib/test/test_string.py
--- a/Lib/test/test_string.py	Fri Feb 17 19:58:41 2012 -0500
+++ b/Lib/test/test_string.py	Sat Feb 18 12:51:49 2012 +0100
@@ -38,6 +38,9 @@
         self.assertEqual(fmt.format("{0!s}", 'test'), 'test')
         self.assertRaises(ValueError, fmt.format, "{0!h}", 'test')
 
+        # issue13579
+        self.assertEqual(fmt.format("{0!a}", 42), '42')
+
     def test_name_lookup(self):
         fmt = string.Formatter()
         class AnyAttr:
diff -r 47288880cc9e Misc/NEWS
--- a/Misc/NEWS	Fri Feb 17 19:58:41 2012 -0500
+++ b/Misc/NEWS	Sat Feb 18 12:51:49 2012 +0100
@@ -7067,6 +7067,8 @@
 Library
 -------
 
+- Issue #13579: string.Formatter now understands the !a conversion specifier.
+
 - Issue #7071: byte-compilation in Distutils is now done with respect to
   sys.dont_write_bytecode.
 
@@ -7555,6 +7557,7 @@
 
 - Windows locale mapping updated to Vista.
 
+
 Tools/Demos
 -----------